Hi Peter,

Is it possible the tape had been reshelled at some point, or some 
combination of parts assembled together?

Tim Gillett,
Western Australia

----- Original Message ----- 
From: "lists" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, September 11, 2018 6:14 AM
Subject: [ARSCLIST] very strange/unique decay found on u-matic

Today I received a " u-matic tape with the strangest damage I have ever
seen and was wondering if anyone else had seen something similar or had an
idea what might have caused it.

We have processed nearly 500, 000 tapes and we do quite a lot of disaster
recovery.  I have seen tapes that have been exposed to virtually every
negative influence imaginable (and some not so imaginable) so I was quite
surprised to see something totally new.

The tape:

The tape is a 3M UCA-60 from 1984.  The cassette and hubs are white(ish)
plastic and the interior posts/guides and the door lock mechanism are made
out of black plastic.  The access door is anodized black metal.

The damage:

The tape is entirely discolored where exposed. The discoloration is only
near the edges a few wraps into the tape.  I have not spooled  the entire
tape yet to determine how far the discoloration continues.  The metal
cassette access door shows many small spots of corrosion on the inside of
door where it would be closest to the tape.  There is no corrosion on the
outside or the edges of the door. The tops of the metal screws on the back
of the cassette are badly corroded.  The entirety of the black plastic tape
guides and black plastic door lock mechanism are very brittle/damaged, to
the point where they are falling apart and partially missing/destroyed.
There is no other indication of damage. The white plastic shell and tape
hubs are intact and clean and the plastic slip pads inside the cassette are
undamaged.  There is no staining, no warping, no breakage and no brittleness
anywhere else. Whatever happened, only the exposed tape and the black
plastic tape guides, the black plastic door lock, the inside of the metal
access door and the metal screws were affected.  Everything else looks fine.

The damage to the tape "could" be consistent with either exposure to liquid
or heat,  but-  there is no staining anywhere or damage to the paper label
to indicate liquid contamination and there is no brittleness or
deformation/melting anywhere else to indicate exposure to high heat.  The
overall damage is not really consistent with either liquid or high heat
damage. I even considered the unlikely possibility that the tape was
contaminated with some corrosive element during playback/rewind and the
posts were damaged as the tape was wound into the cassette.  This could
explain why plastic guides are nearly destroyed and the metal access door
was only corroded inside, near the tape, and nowhere else.  This,
unfortunately,  doesn't explain the corrosion on the screws and heavy damage
to the plastic door lock mechanism, however, since neither of these parts
ever touch the tape.  The plastic hub flange and slip pads inside the
cassette, which do contact the tape, are also undamaged.

Ok, how about some highly corrosive gas that reacts very aggressively with
one specific type of plastic (the guides and door lock mechanism) and
uncoated metal (the screws) but doesn't react at all with any of the other
plastics in the shell/ hubs/slip pads and/or with anodized metal and reacts
differently with the plastics in the tape (or maybe the metal in the tape?)
in such a way as to produce a byproduct that corrodes nearby anodized metal
(the inside of the cassette door) but dissipates quickly (so the rest of the
anodized cassette door is unaffected).  Sound crazy?  Yes it does.  The
damage is so very specific and selective that I can't figure out what could
have happened.

Any ideas?  Magic?  Space aliens?

A very perplexed

Peter Brothers
[log in to unmask]
Audio and video restoration and re-mastering since 1983

This email has been checked for viruses by Avast antivirus software.